274.3 🏥 內科專科考前版

274.3.1 Mechanistic Deep Dive

274.3.1.1 Wavefront of Necrosis

  • Begins subendocardial, propagates transmural
  • 6-12h time window for salvage
  • Final infarct size = function of duration of occlusion + collateral flow + preconditioning

274.3.1.2 Reperfusion Injury & Microvascular Obstruction (MVO)

  • MVO present in 30-50% of pPCI patients
  • Detected on CMR by hypoenhancement on first-pass perfusion
  • Independent predictor of LV remodeling, MACE
  • Treatments tried: cyclosporine (CIRCUS neg), remote ischemic conditioning (CONDI-2 neg), supersaturated O2 (SSO2)
  • Intracoronary low-dose thrombolytic (T-TIME trial — neg)

274.3.1.3 Hibernation / Stunning

  • Hibernation: chronic hypoperfusion → reversible ↓ function; viable myocardium → revascularize
  • Stunning: post-reperfusion transient dysfunction → recovers
  • Viability imaging: stress-rest nuclear, dobutamine echo, CMR LGE
  • STICH trial 2011 — CABG + OMT > OMT alone in EF ≀ 35% (10-yr STICHES)
  • REVIVED-BCIS2 2022 — PCI in ischemic CM did NOT benefit — challenges revasc paradigm

274.3.2 Recent Trials & Updates

274.3.2.1 COMPLETE (2019)

  • N = 4041 STEMI multi-vessel
  • Complete revasc vs culprit-only
  • MACE ↓ 26% with complete revasc
  • Staged within 45 days OK
  • Established complete revasc as standard

274.3.2.2 CULPRIT-SHOCK (2017)

  • N = 706 cardiogenic shock + multi-vessel
  • Culprit-only PCI vs immediate multivessel PCI
  • Culprit-only had lower 30-d death/RRT (45.9% vs 55.4%)
  • Counterintuitive — overwhelms with contrast, instability
  • Class I: in shock, do culprit only first

274.3.2.3 EMPACT-MI (2024)

  • N = 6522 post-MI with congestion or EF < 45%
  • Empagliflozin vs placebo
  • ↓ HF hospitalization, no mortality benefit
  • Class IIa post-MI with LV dysfunction

274.3.2.4 DAPA-MI (2023)

  • Dapagliflozin post-MI in stable patients (mostly without HF/DM)
  • ↓ cardiometabolic events; ongoing for hard outcomes

274.3.2.5 PARADISE-MI (2021)

  • Sacubitril/valsartan vs ramipril post-MI with LVEF ≀ 40%
  • Numerically lower events, NOT statistically significant
  • Reasonable choice but not mandated

274.3.2.6 REDUCE-AMI (2024)

  • Long-term β-blocker post-MI with normal LV function
  • No mortality benefit beyond 1 year
  • May challenge lifelong β-blocker in preserved EF

274.3.2.7 EARLY-MYO (2018), BRAVE-4

  • Microvascular obstruction studies

274.3.3 High-Yield Specialist Points

274.3.3.1 Specific MI Types

Right Ventricular MI (RV MI): - Inferior STEMI + V4R STE - Triad: hypotension, clear lungs, JVD - Treatment: aggressive IVF, AVOID NTG / morphine / diuretic, inotropes if needed, urgent PCI of RCA - Prognosis worse if shocked

Posterior MI: - ST↓ V1-V3 + tall R waves - Posterior leads V7-V9 STE - LCx or RCA territory - Often missed; need posterior leads

STEMI with LBBB: - Sgarbossa criteria: - Concordant STE ≥ 1 mm (5 pts) - Concordant ST↓ ≥ 1 mm V1-V3 (3 pts) - Discordant STE ≥ 5 mm (2 pts) - Modified Sgarbossa (Smith): STE/S ratio ≥ 0.25 (more sensitive)

STEMI with Paced Rhythm: - Similar Sgarbossa rules apply - Hard to diagnose

Spontaneous Coronary Artery Dissection (SCAD): - Young women, pregnancy/postpartum, FMD - 1-4% of all MI; up to 35% in young women - Conservative management preferred (high re-dissection risk with PCI) - Avoid stress tests, anti-platelets debatable

274.3.3.2 Late-Presenting STEMI (12-48h)

  • OAT trial (2006): routine PCI of occluded artery > 24h post-MI did NOT benefit
  • Limited to symptomatic ischemia, large viable myocardium, instability

274.3.3.3 Microvascular Obstruction (MVO) on CMR

  • Predicts mortality, HF, MACE
  • “No-reflow” phenomenon clinically
  • Treatments: ↑ door-to-balloon, intracoronary vasodilators, thrombus aspiration if large burden

274.3.3.4 Stem Cell / Regenerative

  • Multiple negative trials (REPAIR-AMI, BAMI)
  • New approach: iPS-derived cardiomyocytes (BIOSTAR-CMS — early phase)

274.3.3.5 Genetic Testing

  • For familial hypercholesterolemia
  • LP(a) screening once
  • Pharmacogenomics for clopidogrel (CYP2C19 2 / 3) — alternative P2Y12 preferred

274.3.3.6 Bleeding Management

  • DAPT bleeding: hold P2Y12 minimum, ASA if must
  • DAPT + AC in AF: triple therapy 1 mo → DOAC + P2Y12 (drop ASA) per AUGUSTUS, ENTRUST-AF-PCI, RE-DUAL PCI
  • AUGUSTUS 2019: apixaban + P2Y12 (drop ASA) safest

274.3.3.7 Cardiac Rehab Post-STEMI (see Ch274)

  • Class I recommendation
  • 36-session program reduces mortality, recurrent MI, readmission
  • Underutilized

274.3.4 Pearls

  • Time is muscle — every 30-min delay ↑ mortality 7.5%
  • Radial access preferred (MATRIX, RIVAL)
  • EMPACT-MI 2024: empagliflozin enters post-MI armamentarium
  • DAPT + AF: AUGUSTUS — apixaban + P2Y12 (drop ASA after 1 wk-1 mo)
  • CULPRIT-SHOCK: in shock, do NOT do complete revasc upfront — culprit only
  • COMPLETE: in stable STEMI MV, do complete revasc
  • Sgarbossa for LBBB STEMI — memorize
  • OAT trial: do not open chronic total occlusion routinely